Hundreds of people have rallied in Dublin to call for a change to Ireland's abortion laws after a rape victim said she was refused a termination and instead gave birth by caesarean section.

The young migrant's case has reignited a debate about Ireland's abortion laws, among the most restrictive in Europe, which sparked large protests before Parliament voted to allow limited access to abortion for the first time last year.

"I'm here because I was horrified. This poor girl suffered because she didn't understand the convoluted, stupid system here in Ireland," said Aoife McLysaght, a 38-year old science professor, holding a sign saying "forced pregnancy is torture".

"We are trying to put pressure on the government, but it seems to be one of those things they'd prefer to ignore. I feel it's only a matter of time before this law is changed. I just want that time to be sooner so fewer people suffer."

The young foreign national, who cannot be named for legal reasons, told the Irish Times she became pregnant as a result of a rape that took place before she arrived in Ireland.

She sought help to end the pregnancy when she discovered she was expecting, but was turned down by medical authorities. While Irish women seeking abortions typically travel to Britain, which has less restrictive laws, the woman said she did not have enough money to do so.

Under the Protection of Life During Pregnancy Act, which was passed a year ago after the death of an Indian woman who was refused an abortion, a pregnancy can be terminated if the life of the mother is in danger, including by suicide.

The woman said she had attempted to commit suicide, but was interrupted. But by the time she was assessed by a psychiatrist, she was told her pregnancy was too far advanced to halt it.

Protesters gathered in central Dublin on Wednesday and chanted "repeal the eighth" in reference to the eighth amendment to the constitution which followed the passing of a 1983 referendum giving the unborn an equal right to life as its mother.

A United Nations human rights committee told Ireland last month it should revise its abortion laws to provide for additional exceptions in cases of rape, incest, serious risks to the health of the mother, or fatal fetal abnormality.

The committee's chairman, Nigel Rodley, said Irish law treated women who were raped as "a vessel and nothing more".

Ireland's Health Service Executive said in a statement it could not comment on the circumstances of the case until after an investigation, which will be completed by late September.

Prime Minister Enda Kenny's government has indicated it does not plan to address the issue before the next general election, due by early 2016. It would need to hold another referendum to amend the law.

The Pro Life Campaign group said the clamour for wider access to abortion laws was obscene and a chilling and disturbing reminder of the inhumanity of legalised abortion.